2691721 has 2 divisors, whose sum is σ = 2691722. Its totient is φ = 2691720.

The previous prime is 2691719. The next prime is 2691739. The reversal of 2691721 is 1271962.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2673225 + 18496 = 1635^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 2691721 - 2¹ = 2691719 is a prime.

Together with 2691719, it forms a pair of twin primes.

It is a Chen prime.

2691721 is a lucky number.

It is a nialpdrome in base 12.

It is a self number, because there is not a number n which added to its sum of digits gives 2691721.

It is not a weakly prime, because it can be changed into another prime (2691701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1345860 + 1345861.

It is an arithmetic number, because the mean of its divisors is an integer number (1345861).

2^2691721 is an apocalyptic number.

It is an amenable number.

2691721 is a deficient number, since it is larger than the sum of its proper divisors (1).

2691721 is an equidigital number, since it uses as much as digits as its factorization.

2691721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1512, while the sum is 28.

The square root of 2691721 is about 1640.6465189065. The cubic root of 2691721 is about 139.1051944235.

The spelling of 2691721 in words is "two million, six hundred ninety-one thousand, seven hundred twenty-one".